Cabin pressure control



'April 17, 1951 w B KLEMPERER CABIN PRESSURE CONTROL 4 Sheets-Sheet 1Filed April 6, l942 I Arrow/5x April 17, 1951 w. B. KLEMPERER CABINPRESSURE CONTROL 4 Sheets-Sheet 2 Filed April 6, 1942 mmvroa' WogwlvadKzzn/piese llll H1 W. B. KLEMPERER CABIN PRESSURE CONTROL April 17,1951 Filed April 6, 1942 v 4 Sheets-Sheet s r\ r @q a a g 12 v I 4 i'--*IM.

INVENTOR. WOLFGANG 5. fI2MPP5Q A TTOR/VE).

W. KLEMPERER CABIN PRESSURE CONTROL 4 Sheets-Sheet 4 Filed April 6, 1942.Q&

Patented Apr. 17, 1951 Wolfgang Bu Klemperer, ngela s, Calif, as.-

signor to Douglas Aircraftfi companmdnc Santa Mbni'ca Calif.

- Application Apr-ire, 1942',- Serial'No..437,921

48 Claims. :(c1...9s,;-1;s)'

My invention relates toaircraft pressure-cabins and more particularly toapparatus for controlling and regulating the pressure. therein.

Generally, a pressure cabin a livable compartment, in which; the.-airpressure. is artificially controlled and regulated at values suallyabove the ambient atmospheric pressure prevailing; at flight; altitude.The pressure cabin is; nt,,,as a rule, hermetically sealed, inasmuch asmeans are required. both to'take-aipinto-and; to exhaust air from thecabin in order; to maintain-a livable pressure while the aircraft,flies,;:through high strata of. air too thmicrsafely sustain nere pi aetion. Moreover, these means are. capableof establishing pressureequalization prior mland- If a cabin shellis constructed sumeiently;strong to; permit sea level pressure o e maintained therein at any;altitude the particular aircraft can attain, the only pressureregulation roblems are those caused by differences of altitudes at thepoints of departure andarrival! cabinsoconstructed would of necessity berather-heavy and thereby reduce the economic efficiency of the aircraft.

Most aircraft passengers, however, can readily tolerate altitudes'in therange of 5,000 to 10,000 feet, and, in. view of this fact, it isstructurally and mechanically advantageous to design apressure cabin fora certain moderate pressure. differential. It is then desirable togradually reduce the cabin pressure during ascent at a, lesser apparentrate of climb than that of the aircraft, but in a manner such that thepermissible. pressure differential is never exceeded, Similarly, duringdescent, the cabin pressure-may be gradually raised in order to equaltheexistingambient atmospheric pressure, shortly before landing,

The principal object of my invention. is to provide an aircraft cabinpressure control: system which complies with such limitations of permis-Anotherobject is to minimizethe rate of pressure changes to whichoccupants of the cabin are subjected while the aircraft climbs ordescends at a high rate or encounters bumpy air. Stillanotherobject isto provide such a rate of pressure change control means which, subjectto a preselected differential pressure limit, will permitior; induceachauge of pressure within .the

cabin, whetheran increase-or adecrease-at a,preselectedrateandregardless of the change or rate ofchange-of ambientor flight altitude pres- .Furtherobjectsware: to provide a system for,controlling. the pressure-within a cabin; to prouidaa-control forautomatically and/ or manually regulating the pressure within a cabin;and to .provide, an altitude-ratio mechanism for con- -trolling; thepressure within a cabin. Still further cbjects; are; toprovide mechafor-m'inimizing the rate and/or degree of ,cabin pressure changes; toprovide adjustable .mechanismfor setting the altitude above which thepressure cabin shall operate; and to provide a relatively rugged,inexpensive, and efiicient ,cabinpressure control system. Other, andfurther objects will become apparent as the description proceeds.

For a clearer understanding of my invention, referencev may be had tothe drawing in which:

Fig. 1 is aperspective schematic view of an embodiment of my cabinpressure control system, a fragmentary portion of the aircraft beingshown in phantom; ,-.Eig 2 is a partially sectional and partiallyschematic view-of components of the pressure ,control system-including acabin pressure regulator, lag, control, cabin rate of climb meter, cabinaltimeter, and the electrical system for controlling cabin outletvalves;

, Fig-: 3 is a sectional view of another-embodimentof a cabin-pressureregulator;

sible pressure differences between the interior of Fi g a is a"sectional view of a. third embodithe cabin and the ambient or flightatmosphere as may be dictated bypassenger comfort,- strength ;-i;nent-ofa cabin pressure regulator;

- Fig 5.-"1S' a schematic diagram, of an outlet valve considerations orlimitations 'of compressor limitswitchsystemiorcontrolling-blowerair-de- Another object is to provide a, pressureregulating system which will eflect changes in cabin d-ifierentialpressure inversely proportional -to changes in flight altitude pressureofzthe aircraft. 1

A further object is to provide a pressure re l lating system which willeffect changes in cabin livery:

;6 isa partially I-sectional and partially schematic view of a pressureregulating system including a cabinrateof climb .meter and a cabinaltimeter, the cabin pressure; regulator of Fig. 2 beingrenderedinoperatireinthisembodiment.

Referring: now to the drawings. an-airplane-G having wings, fuselage,controlsurfacespower absolute pressure directly proportional tochaneesplant, etc. is equipped witha cabin 8: adaptedto in flight altitudepressure or the aircraft;

withstand a desirable pressure. differential or,

lead directly to the blowers l0, and therother one leads directly to thecabin duct system. The latter conduit is the largest of thethreeandincorporates a check valve l5 which is adapted. to

close the aft portion of this duct to incoming air as soon as theblowers begin operating and build.

up a pressure in the cabin greater than the flight.

termed the equalizing altitude from which the pressure differential isbuilt up as the airplane ascends.

The regulator 24 comprises a case 26, the interior of which is subjectedthrough the conduit I30 to the absolute pressure within the aircraftcabin. The case 26 houses a pair of coaxially mounted pressuresensitive'units 28 and 30. The unit 28 is anevacuated'bellows or aneroidand is responsive to changes in the cabin absolute pressure. The unit 38is a capsule exteriorly subjectedtto cabin pressure while the interiorthereof is connected by conduit 3| to ambient flight pressure. Thiscapsule thus is responsive to changes in the difference between cabinabsolute pressure and ambient flight pressure that is responsive to rampressure. In fact, my invention is such that" thereneed be no differencein the distribution of fresh air or its temperature control mechanism,whether or not the cabin is supercharged. In orderto accomplishsupercharging or pressurizing, however, it is necessary that the cabin,cabin air exhaustvalves, ducts and other associated parts be designed towithstand a pressure d ference.

The controlled cabin air outlet valves I2, l2 are supplemented by largeroverhead exhaust outlets '18 for discharging sufl'icient vitiated airfrom the cabin and lavatories in unsupercharged flight. These largeoutlets are especially needed to insure ample ventilation in hotweather. While I have shown only two controlled cabin air outlet valvesplurality of these valves, differently located, is

advantageous because, when flying supercharged,

it is desirable to exhaust the air mostly from the lavatories ordressing rooms which may be situated at opposite ends of the cabin.

When ascending, and desiring to supercharge,

the large outlets [8 are closed and the quantitative outlet control isturned over to the smaller valves I2, l2 which can b -more accuratelyregulated and which preferably discharge into such unsuperchargedfuselage portions as baggage and cargo compartments, thereby not onlyheating these portions but also precluding the possibility of icingoccurring in the outlets. The control of the valves l2, I2 can beoperated manually as by a handle 28 in case of emergency, but normally'thiscontrol is effected automatically by a servo systemfbroadlyreferred to as 22, which is responsive to or controlled by a cabinpressure regulator 24.'- I

' The present preferred-embodiment of such a cabin pressure regulatoris, in efiect, an altituderatio control which tends to regulate orchange thebabin absolute pressure directly proportional to changesin'ainbient flight pressure. In most casesj aiflight schedule isprepared before take-ofi whereini-is determined the altitudes which theairplane will attain and the altitudes at which the airplane Willcruise,and the cabin pressure regu- :lator can be adjusted accordingly to setthe cabin supercharger system in operation when desired.

-Up untilthe time'the supercharger system be-.

While I have shown in Figure 2 the changes in cabin differentialpressure.

A contact arm 32 is pivotally connected at its one end 34 to a bracket36 fixed to an irmer wall surface of the case 26. This arm is alsopivotally connected intermediate its ends at 38 to an extensioncoaxially carried by the aneroid 28. The free end of the contact arm" 32is disposed between a pair of spaced contacts 40 and 42 and this end asthe arm is'pi'votally moved because of expansion or contraction ofthepressure responsive units 28 and 38, will move between and intoengagement with'one-or-the other of the spaced contacts 40 and 42. 4

To indicate theregulatorsetting a scale 44, together with an index, notshown, i provided on the face of theinstrument. QAdjustment of theregulator, that is the settin'g of the equalizing altitude,is-accoinplished by a knob 46 fixed to the outer end of a-" small shaft41 rotatably carried by the one wall of the case 26. The inner end ofthe shaft 41 is threadedly engaged in a tapped opening forn'iedin theone-wall of a slide member 48 'held' against "rotation. The slide member48 carriesthe contacts 40 and 42 and it will beseenthat as: the shaft 41is rotated the slide member 48 will move in one'direction or the otherdepending upon the direction of rotation of the shaft". This movement ofthe slide member 48 obviously will vary the position of the contacts 40and 42 relative to the end of the arm 32 disposed between the same. Thescale 44 is formed about its edge face as clearly shown in Figure 2 witha plurality of teeth to permit the scale to be driven through the pinionshown mounted to the shaft 41. Y preferred embodiment of the regulator24, the arrangement may also be such 'that the contacts 40' and 42 arefixed and the fulcrum of the lever arm 32 adjustable relative thereto,as shown in the form of the regulator illustrated by Figure 3.

In addition to this embodiment, there are at least two otherinterchangeable and feasible adaptations of the two pressure sensitiveunits 28, ;38, the common feature of all three being that cabinpressure,f flight altitude pressure and their "diife'rence are effectiveupon the instrument. fQne of these other adaptations is shown in Fig.

3, "wherein the 28, 30 perform the same function as in Fig 2 but are nolonger superposed "andthere'fore may be of different sensitivity as willbe later explained. The third' adaptation is shown in Fig. 4 wherein theunit 28 is of the same 'type as in Figs. 2 and 3, that'is' an aneroid,but is now responsive to flight altitude pressure, and the unit 30 is apressure capsule exposed to the pressure differential between flightaltitude pressure and cabin absolute pressure, the flight altitudepressure being connected into the regulator case through the conduit andthe cabin pressure being connected to the interior of the unit-'30 bythe conduit I30;

If an altitude ratio control of, say, 1 to 2 is desired, that is, cabinpressure controlled substantially halfway between flight altitudepressure and equalizing altitudepressure, and if the sensitivity of thetwo regulator units is alike, they can be merely superposed asshown inF-ig. 2. If, however, the sensitivityis not the same, a lever systemsuch asthat shown in Fig; 3 must b introduced for connecting the units28, 30 to the lever arm 32 in order'to' obtain the desired 1 to- 2ratio.

The regulator in efiecting control of cabin absolute pressure performsthree functions, one at a time;- it may energize avalve closing-circuit49 of the servo system when an increase in cabin pressure is needed; orit may energize a valve opening circuit 50*oithe servo system whencalling for a decrease of cabin pressure; or it may energize neither theincrease nor decrease circuits when the cabin pressure is substantiallythe pressure called for by the predetermined ratio of flightaltitudepressure to cabin pressure.

The regulator-2 k controls theservo system 22 through the arm 32 as thesame is pivotally moved in response to the changes in the pressures towhichunits 28 and- 30 are subjected. This control action is effected bythe end of the lever- -32- which moved into and out of engagement withthesp'aced contacts-40 and 42. The conta'ct'lil forms'a part'of thevalve closing circuit 49 while contact 42 is connected into and forms apart ofvalve opening circuit 50. The arm 32 is electrically connected toa lead 32c which may be called the'grounding conductor for the regulator24.

The servo system-includes an-electric motor of the reversiblesplit fieldseries type adapted to drive, in either direction, suitable gear trainsoperatively connected to move the valves [2. The motor 5l- 'may beoperated by energiz'ation of either a field coil circuit 52 or a fieldcoil circuit 53 from some suitable power source such as a battery 54 toopen or close the valves l2 depending upon the direction of rotationofthe motor.

As will be hereinafter shown, the directional control of the motor andconsequently the valves l2 may be effected through movement of thecontact arm 32 as it is pivotally moved because of contraction orexpansion of the pressure units 23 and 30 in response to changes in thepressures to which these units are subjected.

The servo system 22' also includes a relay 55, which is essentially apowcr'amplifier in that very small currentsfrom a, battery 56 can beused to bring about a flow of relatively large current in the motorfield circuits 52 and 53 respectively. Thejre'lay 55comprisesftwo fieldcoils 51 and 58 connected respectivelyto the control circuits at and s9.Energiz'ation' of-the contrclcircuit andits coil '58 will" cail s e thearmature 55 of 'the relay 55 to'mo've into engagement with a contact '58connected into the motor field circuit 52 to energize the same.Energization of the field coil circuit 52 causes the motor 5| to drivethe discharge valves [2: towards closing position and similarlyenergization of the control circuit 50 will cause the armature 59 tomove into engagement with a contact SI of the field coil circuit 53 toresult in energization of that circuit to bring about opening movementof the discharge valves [2. The two centering springs not only hold thearmature 59 in the balanced or centralposition' as shown in-Figurc 2 inwhichneither control circuit is energized, but are also effective tomovethe armature 59 into its center position whenever both control circuitsare simultaneously energized.

To prevent overloading of the contacts forming apart of control circuits49 and 50, an electronic relay schematically indicated at 62 may beused.

At high altitude the position of the outlet valves can serve to indicatethe air flow rate. Consequently a servo control can be attached to theoutlet valve mechanism to be actuated when the valves open or closebeyond two or more set stations. A motor 68 actuated by this control isprovided for each blower 10 to decrease or increase theflow of fresh airby more or less throttling the flow or by slowing down or speeding upthe blowers.

The principle of operation of all embodiments of the regulator hereinshown and described are thesame. For example, if the equalizing altitudeof the instrument is set at 2000 feet, the contact arm 32, so long-asthat altitude is not exceeded, will be held by the aneroid 28 inengagement with the contact 42. Engagement of the arm 32 with thiscontact, it will be remembered, results in encrgization of the-valveopening relay coil so that the valve [2 will be held open to equalizecabin pressure with ambient flight pressure during ascent ofthe airplanefrom a landing field to an altitude of 2000 feet. As the aircraftapproaches 2000- foot altitude, the aneroid 28 in expanding will movethe contact arm 32 out of engagement-with the contact 42 and as the 2000foot altitude is reached the now further expanded aneroid will move the.arm into engage ment with the contact 40. Whenthe arm'- 32 is engagedwith the contact 40, the valve closing relay is energized to bring aboutclosing movement of the valve l2. Asthe valve is moved toward its closedposition, cabin absolute pressure will consequently increase and theincreasing pressure tends to collapse the aneroid 28 to move the contactarm 32 away from contact 40. Disengagement of the arm 32 from contact 40arrests further movement of the valve and if cabin absolute pressurefalls below the equalizing pressure of 2000 feet, as the aircraftascends beyond that altitude, the arm 32 will again move into engagementwith the contact 40 to again increase cabin absolute pressure. It willthus be seen that the aneroid 28 seeks to maintain cabin absolutepressure substantially that of the pre selected equalizing altitude asthe aircraft ascends beyond that altitude.

If the aneroid 28 was the only instrument controlling operation of thevalve I2, cabin pressure would be maintained substantially constantunder the control of that instrument. The differential pressure capsule30, however, is also operatively connected to control the valve 12 andonce the--aircraft-has ascended beyond 2000 feet altitude, increasingcabin differential pressure brings about a collapsing movement of thedifferential capsule 30 in opposition to the force produced by theexpanding aneroid. It will thus be seen that the position of the arm 32is conjointly controlled by the aneroid 28 and the differential pressureresponsive capsule 30 to so vary the rate of air discharge from thecabin that cabin absolute pressure changes in direct proportion tochanges in ambient flight pressure.

Highrates of climb or descent of the airplane may be encountered whenthe pilot maneuvers over or under clouds, or when vertical air cur- 7rents in an unstable atmosphere carry the airplane up or down; then eventhe fractional rate of climb or descent apparent in the cabin, asgoverned by the pressure regulator, may be too rapid for physiologicalcomfort. To avoid this a lag control incorporated in the flight altitudepressure conduit 3| makes it possible to produce a lag between thechange of flight altitude pressure and cabin pressure. This controlconsists of a thermally insulated air volume bottle 12 and a needlevalve 14. The bottle 12 functions to decrease the pressure sensitivityof the ambient pressure in the conduit, the thermal insulationpreventing sudden cabin temperature variations from inducing erratic airpressure variations within the bottle. The valve 14 controls the amountof opening in the conduit 3| and consequently the amount of response toflight pressure changes on the part of the unit 30. When the lag valveis wide open no lag in pressure change is effected and the unit 30follows quickly the outside pressure changes at the flight pressure tocabin pressure ratio. If the lag valve is tightly closed, the flightpressure unit 30 of the regulator becomes inoperative, the regulationthen tending to maintain constant absolute cabin pressure. When the lagvalve is partly closed, the action is intermediate and the cabinpressure eventually follow flight altitude pressure changes toward thepredetermined ratio, but with some lag inasmuch as the air can butslowly escape into or out of the regulator until considerable backpressure develops. Thus, sudden flight altitude changes of shortduration are smoothed out and kept from appreciably affecting the cabinpressure, whereas prolonged altitude'changes will be followedeventually.

As previously mentioned, it is possible to vary the ratio of cabinpressure to flight pressure control within reasonable limits. One methodof accomplishing such a ratio change is illustrated in Figure 4. In theratio control instrument of this embodiment, an adjustable fulcrum isprovided between the lever arm 32 and a connecting rod 63 pivotallyinter-connecting the pressure responsive units 28 and 80. The fulcrumadjusting mechanism may comprise a roller 64 adapted for rollingmovement along the rod 63 to thus vary its position relative to thelever arm 82. The roller is actuatable by a knob 65 carried by a stubshaft 66 rotatably extending through the case of the regulator. Theinner end of the shaft 66 is threadedly engaged in a bore of a boss 61pivotally connected to the pushpull rod 68 carrying the roller 84. Theprinciple of such a ratio changing mechanism is to vary the relativeefiectiveness of the pressure units 28 and 30 which principle obviouslymay be accomplished in various ways.

The system thus far described is sufficient to accomplish certain of theobjects of the invention. However, I have also incorporated in thesystem a cabin rate of climb meter 16 and cabin altimeter I8 which maybe used at will to make supercharging functions more flexible undercertain operating conditions. The cabin rate of climb meter may be usedin conjunction with the cabin altimeter to accomplish supercharging moreor-less manually, in which case the reg- .ulator 24- is disconnectedfrom the electrical hookup by a switch 80 and the system then isessentially as depicted by Fig. 6. This system will be later described.

In addition to the cabin rate of climb meter 16 may be used inconjunction with the lag valve 14 and for a similar purpose, in whichcase the cabin altimeter is disconnected from the electrical system by aswitch 82. The cabin rate of climb meter 16, fully illustrated in Figure6 but only schematically shown in Figure 2 is exposed to cabin pressureand is connected into the electrical hookup by a switch 84. The meter isof the conventional type except that its pressure sensitive unit,designated by the numeral 85, is adapted to actuate a lever 81 insteadof an indicating needle. Also, a pair of spaced electrical contacts 86,88 are provided, the separation of which can be adjusted by a knob 90.When the contacts are widely separated, the meter does not interferewith quick response of the cabin pressure to flight altitude pressurechanges in that the lever is unableto touch either of the contacts 86,88 before an extensive change has taken place. However, when thecontacts are closely adjusted, the meter does interfere because thelever touches one or the other of'the contacts more quickly dependingupon the distance between them, thereby opposing any rapid cabinpressure changes.

In addition to the possible adjustment of the contacts relative to eachother by means of the knob 90, another knob I04 is adapted to move bothcontacts relative to the lever,,and this knob is geared to the rate ofclimb meter dial for setting the desiredrate of climb or descent.Contact 86 may be termed the cabin climb or pressure decrease rate limitcontact, and 88 the cabin descent or pressure increase rate limitcontact, the device being so arranged in the outlet valve controlsystem, as shown in Fig. 2, that in the event of regulator 24 demandingan increased cabin pressure and the rate of climb meter 16 demanding alower pressure, relay 55 will balance and open both circuits, therebystopping or damping the valve action in response to the speed of climbor descent. For example, if it is desired to adjust the equalizingpressure of the regulator 24 to a higher equalizing altitude, the outletvalves I2, l2 would immediately begin opening in order to seek the newratio between cabin pressure and flight altitude pressure. As the cabinpressure rises, the rate of climb meter 16, being responsive to the rateof cabin pressure change, will actuate the system through the cabinclimb limit contact 86 if the rate of ascent is in excess of the setlimiting rate of climb, which limit is determined by the distance thatthe ascent limit contact is set from zero. This would in turn cut outthe valve opening circuit of the outlet valve control. Conversely, ifthe equalizing pressure setting of the regulator is lowered, the systemis actuated by the cabin descent limit contactof the meter when the rateof descent is excessive, and the valve closing circuit is cut out.

To more fully explain the operationof the rate of climb meter 18 in thesystem disclosed in Figure 2, it will be seen that contact 86 iselectrically connected to the control circuit 49 by a lead 86A. Thecontact 88 and the control circuit 50 are electrically interconnected bya lead 88A. As the lever arm 81 is electrically connected by a lead 81Ato the grounding conductor 32A, it will .be seen that the meter 16 canalso control energization. of the relay 55.

If in any flight of the aircraft, the ambient flight pressure isincreasing or decreasing at such a rate that the regulator 24 ineffecting its ratio control brings about a rate of pressure changezumaeeo ment with the contact 42 to energize thecoil. 51 of the'relay 55to bring about opening movement of the valves 12 and theipressure-withinthe'cabin begins to decrease at a rate-.in excess of the preselectedone, the arm 81 of'the. meter '16 wil move'into engagement. with thecontact 88 and thus also energize the.coil.58 of the relay 55. Aspreviously explained, the. centering springs, when both coils of therelay J55 are. energized, will move the-armature 59. into its center. orbalanced position. between the. contacts 60' and GI. This movement ofthe armature obviously results in de-energization .of the motorfield-circuits 52 and 53 to arrest further movement of the valvesv l2and consequently further increase in the rate of pressure. change withinthe'cabin;

Itcan also be-pointed-out that ifthe. contact arm 32' isdisposedbetween, that-.is, engaging neither of thecontacts-MI- and. 42,therate of .climb meter can' then act-as a primary control and. willbring about movementof the valves. l2

'to-prevent a rate of pressure. change.-in.excess of the. preselectedone.

Both themanually operated lag mechanism and the:cabin rate of. climbmeter are utilized for causing the cabinpressuratofollow the flightaltitude. pressure in. a ratio .reduced-fromrthe predetermined regulatorcontrolledratioif the.flight altitude. change istoo" rapid. for.physiological comfort.v Both. theselagdevices may be used simultaneouslyin flight altitude communication to. the regulator, thereby providing:not. only a positive rate of. climb and-descent limit or :pressure.decreaseand. increase. limit,- butalso a nominal lag forsubstantiallyeliminating; cabin pressure changes during temporary-- and; rapid flightaltitude pressure changes. Either lag or damping device can be setbefore take-off and reset at any time during flight.

As previously stated, in order to control:.the superchargingv of thecabin more flexibly than is:possible with the automaticregulator 24, theelectrical control circuit can be opened by switch 80, whereupontheregulator 24 is rendered inoperative, and the cabinaltimeter. switch82 and rate of climb meter switch 84 are closed, the system thenconforming with Fig. 6.

The altimeter used is of the conventional type except that its pressuresensitive unit, designated by the numeral9l, is adapted to actuatealever 99 instead of the indicator needle ordinarily incorporated insimilar instruments. This lever is providedto close theelectricalcircuitsat con.- tacts 98 -400, the separation of which. canbe adjusted by a knobJDZ. The operating principle with respect.to-thelever and the contacts is identical with.thatof the rate of climbresponsive unit, the difference -between.-the twobeing that. the. rate;of climb unit-1 limits r the rate of increasaanddecrease. of cabinpressure; .whereas the altimeter controls the maximum andminimumpressures inthecabin depending on. the setting of the contacts relativeto. the-lever 99. In addition to the-possible adjustments of thecontaetsrelative to eaehiother by, means of the K110121192, almob;lli'lris provi'ded-to adjust both contacts relative: tothe-lever; This Ilatter knob is geared to the altimeteirdialforrthe contacts to thedesired. altitude: 'Ihe=-term-altitude in thiss-lnstancaahowvevewisused: as. re-

10 ferring to cabin pressure imthat-ifthealtimeter dial is set at!10,000-feet,,the;unit will maintain a: pressure-in; thecabin.corresponding to that found at 10,000-feet aititude-instandard air eventhough theactual; flight. altitude may be, for example; 12,000 feet.

Thecabin-.ratepfclimb meter new functions to limit the cabin rateof:climb or descent or pressuredecrease or: increase-until a cabin pressureequivalent to. the'altitude'previously set on the. altimeter is-.-reached; whereupon the altimeter wi]l--. halt. the: c1imb= or:descent and tend to-maintainthe cabin-pressure constant to thataltitude; In-.-othen words; although the system is.-attempting-to'induceraa change in cabin pressure independently of the actualflight.path of the: aircraft; the= cabin rate: of" climb meter actuatese thedecrease: and. increase servo systems at. theset rate of: speed,, as theairplane climbs and: descends=until .-.the :desired=pressure altitude,as selected; onwthe'r altimeter; reached. When thisaltitudeisireachedsthei altimeter will open or. de.-energize the: decreasecircuitifthe airplane is: ascending) or cutout' the increase circuit'ifthe:airplaaie=issdescending-. No ratios are usedrin thiSmOdeofi-supereharger control, nor are any pressure sensitive unitsnecessary other than-r those customary inrconventional: rate of climbmeterseanjd: altimeterss In: fact, this --embodimentmayabe deseribed'aseffecting aclimb schedule controh asdistinguishedhfrom: thepreviouslydisclosed: al-titudeiratio. control.

Before such a climb schedule controlledsupercharged flight;;,the .cabimaltimeter; upper limit contact-98ais :setr-by,l-theknob\ l01-to themaximum desired-cabinrpressurer altitude; say, 10,000 feet,-.andsthe=c0ntactsr0n thercabinrrateroi filimb meteriarerset byfmeans ofl'alc'nob-l0l to a'definite value,..say;.300 feet, per-:minute.- While theairplane 1 climbing, and, the. supercharging system. is-functioning,the. cabin.- pressure will decrease: at (the set rate until:thesetpressure altitude is attained,:.-at-,whicl time the altimeterlever 9awillrconnect=with contact 98 and, through the servo-system,rwillimaintain: the desired pres- .sure..

When thelcabin pressure conforms with the pressurealtitude. settingthe-cabin rate of climb meter. contacts-815;.8&-may-be;set to zero rateof climb.-and -the;lower. altimeter limit contact 98 and the. higheraltimeter 'limitcontact I 00 may be set-closetogetherrbyjmeans oftheknob I02, therebysubstantially preventing any cabin pressure:fluctuationsinthatthe levers- 81- and 99 wouldiimmediatelyconnectwithone or the other of thein respective contactsand-operate the valvecontrol- .through the servo system..

- When ready to:deseend,',-the lower altimeter limit is reset toi; analtitude-slightly above the field of destination: and-the cabin rate ofclimb meter. contactsare-set: to the desired rate of descent or:cabingpressureincrease; While the airplane-:isdescending; thecabinpressure will gradually rise to and linger at the pressure'of theset altitude until the-flight altitude reaches the samerlevel,at'which-ltime.the supercharging.system. is turnedofi and thecabin isopenedv to ambient atmospheric pressure.

It will thus be seen thatthe system ofthe present invention willin factinduce a pressure change within the cabin even though theaircraftmaybefiyingin levelflight: This is possible with all embodimentsof" the 'system disclosed 61;- as previously'explained; whenevertheregmater-24 01 tlie aitiirleter 1'8 is reset iii stem 'the cabinpressure will tend to reach as quickly as possible the reset pressurevalue, but is prevented from rapidly changing because of the action ofthe rate of climb meter 16. Whether the rate of climb meter I6 isconnected into the system so as to act as a vetoing or over-ridinginstrument or it is so connected that it acts as a primary controlinstrument, it is always operative to limit the rate of pressure changewithin the cabin to the preselected rate.

A number of safety features must be observed in an aircraft cabinpressure regulation system to insure passenger comfort and operationsafety. For example, safety valves I06 are provided in the large exhaustoutlets l8 and are set to relieve if the pressure differential exceedsthe design limit.

Non-return valves I08 are provided in the supercharger delivery ducts toprevent reverse flow in event of acompressor failure. A check valve I isarranged to open and thus prevent any appreciable suction in the cabinwhen the airplane descends to-altitudes below the pressure equalizationaltitude. This valve is preferably located in the ram duct wherein uponstarting to supercharge it will close as soon as the cabin pressureexceeds the ram pressure.

The operation of the automatic pressure differential superchargingsystem as controlled by the regulator 24 will now be described. .ABeforebeginninga"supercharged flight, the operator determines the maximumaltitude the airplane will or may attain, say, 17,000 feet, and fromthis he determines the pressure altitude at which he may supercharge thecabin while at maximum flight altitude without reaching the permissiblepressure differential of, say, 3 pounds per square inch between cabinpressure and flight altitude pressure, and yet obtain a high value ofpassenger comfort. With this maximum differential pressure, in theparticular example above given, the cabin pressure altitude would be9,000 feet. He then determines the equalizing altitude to which he mayset the regulator, assuming that the altitude ratio incorporated in theregulator was already fixed at, say, 1 to 2, for the normal flightconditions over his route. In the case of the above example, thisequalizing altitude would result as 2X9000-17000=1000. If the operatordoes not wish to begin supercharging at this altitude, perhaps becausehis takeoff or landing field may already be situated higher, say, at1500 feet, then he will set his equalizing altitude slightly higher,say, at 2000 feet, and the cabin will then attain a slightly higherapparent altitude, for example, 9500 feet, when the airplane reaches itspeak altitude of 17,000 feet.

If the cabin rate-of-climb meter is connected into the system, thisshould be set as previously described to the desired maximum rate ofclimb and descent or pressure decrease and increase. These settings maybe changed at any time in flight.

As the airplane-ascends to the equalizing altitude, the blowers ID areturned on and the large cabin exhaust outlets 3 are closed, thecontrollable outlets I2, I! remaining wide open. The

lag valve 14 is usually set to minimum lag or fully open.

When the equalizing altitude is reached, the pre sure regulator beginsto move the outlet valves and, With increasing flight altitude, thesevalves gradually move toward closed position. The cabin pressuredifferential rises and when it surpasses ram duct pressure the ram ductcheck valve l5 closes.

A the airplane is leveled off for cruising at relatively high altitude,the cabin pressure remains substantially constant at the predeterminedratio between flight altitude pressure and the set equalizing altitudepressure. The damping control may be set to greater sluggishness tominimiz unintentional cabin pressure changes as the airplane encountersrising and descending air currents, or the cabin-rate-of-climb meter maybe set to lower limits of climb and descent or pressure decrease andincrease.

For normal descent, the damping controls are reset to low lag in orderto allow the cabin rate of descent or pressure increase to follow theflight rate of descent at the predetermined ratio. During descent, ifthe cabin climb meter is inoperative, the lag should be adjusted tosluggish when a temporary high rate of descent of the airplane isplanned. However, if the climb meter is operative, the lag valve may beleft fully open and the rate-of-climb meter will restrain the cabindescent or pressure increase to the set rate. When the set equalizingaltitude is reached, the valve outlets l2, l2 are open, the ram ductcheck valve l5 opens, the blowers are shut off and the large cabinexhaust outlets [8 are opened.

Various departures from normal operation are feasible and are left tothe discretion of the operator when he is confronted with unusualconditions. For example, in climbing it may be desirable to delaystarting the blowers until after the set equalizing altitude pressurehas been pass-ed, in which case the damping of the re lator should beadjusted to sluggish or the climb limits set low while the cabinpressure temporarily increases to its called for value. When the cabinpressure finally begins to decrease, the lag adjustment and/or the climbmeter should be reset to allow the normal flight schedule to befollowed. The operator may also decide to land supercharged, in whichcase he may reset the equalizing altitude slightly below the field ofdestination and reduce the pressure slowly while taxiing.

My p essure regulation system is essentially automatic whilesupercharging and therefore requires none other than normal attention.However, manual emergency control is available at any time and anydegree of semi-automatic control can be adopted if desired; one methodbeing the variation of the equalizing altitude setting and another byhand manipulation of the outlet valves. Also the regulator 24 may beswitched off and the pressure controlled by the rate of climb meter andthe altimeter as previously described.

While I have described my invention in its present embodiments, it willbe obvious to those skilled in the art, after understanding myinvention, that various changes may be made therein without departingfrom the scope thereof. I aim in the appended claims to cover all suchmodifications or changes.

I claim as my invention:

1. In an aircraft cabin adapted. to be super- 13 charged above theambient atmospheric pressure, superc'harging means,- comprising ablower, at least one outlet valve for discharging vitia'ted air from thecabin, a servomotor adapted to control said valve, a regulator operativeto actuate said motor in response to any-departure of cabin pressurefrom a value functionall correlated with flight altitude pressure, meansadapted to vary the functional relation between *flig'ht alti- "tudepressure and cabin -pressure, means adapted to govern the flow ofsupercharging air into said cabin, means adapted to adjust thesaid-regulator to a set equalizing altitude above-which 'superchargingbegins and below which --superchargingceases, means adapted to limit anddelay 'the response of said motor to excessive or sudden variations ofthe functional relation or flight altitude,-mea'ns adapted togovern theflower supercharging air from said cabin, and meansror assuming manualcontrol of said valve *in event of failure of said motor.

"2. In an 'aircrait, a cabin pressure regulating device *for controllingcabin pressure -'altitude at a reduced ratio from flight pressurealtitude, said device including inoperative combination at least twocoacting pressure sensitive units, the first "being responsive to cabinpressure and the secend being responsive to "both cabin pressure andflight pressure, a servo system for controlling cabin air flow, meansfor transmitting the effect of pressure reactions of said coacting unitsto said servo system for controlling saidratio, "and means for retardingthe sensitivity of the second "said unit to flightpressure, wherebysudden'flight pressure variations are prevented from causingcorresponding sudden cabin pressure variations.

Kiln-an aircraft, a cabin adapted to 'besupercharged-a ramming air"intake duct "leading to said cabin, a supercharging blower adapted toincrease the pressure of the incoming air, anoutlet valve adjustable tovary the cabin pressure with relation to the incoming blower pressure, aregulating device sensitive to pressure differences between flightaltitude pressure and cabin pressure and adapted to control said-outletvalve to maintain a predetermined ratio between cabin pressure andflight altitude pressure, as gauged from a set equalizing altitudepressure, a servomotor for-operating-said outlet valve, said servomotcrbeing actuated in response to pressure variations in said regulatingdevice, a second servomotor for varying thedelivery of the superchargerblowers if the valve is unable to adequately control the pressuredifferential, means Within the outlet valve to control the second saidmotor, and an adjustable lag means for preventingrapid changes in'fiightaltitude pressure Irom efiecting a change in cabin pressure at arate toorapid in physiological comfort, said lag means :comprising a valvefor'restr-ictingtheconnection between flight altitude pressure andthe-said regmating device. I

4.111 an aircraft, a cabin pressure regulating ileviceio'r controllingcabin pressure altitude at a reduced pressure altitude-said deviceincluding in operative combinationatleast two-coacting pressuresensitive units-one unitdieing responsive to changes in cabin pressure,the other responsive to changes in the difference between cabin pressureand fiight-pressure means for controlling cabin air flow, meansfor-transmitrthexefitect of pressure. reactions of said coacting unitsto saidoonntrcl' fior controlsaidxatio, :a rate or! vclim'b re'gulating"means In: rlimiting the irate of xlem'ease-"or 'increaselof cabinpressure, and means for setting'the limiting rates, the rate of climbregulating means being adapted to override the controlling influence ofsaid coacting pressure'sensitive'units upon said control means, therebypreventing pressure change in the cabin at a rate in-excess of the setlimiting rates.

5. In an aircrait'a cabin adapted to be supercharged, at least oneblower for supercharging said cabin, atleast one outlet valve-forcontrolling the amount of supercharging, an automatic regulator forcontrolling-said outlet valve, the re ulator comprising -a pair ofpressure sensitive coacting units,one unitbeing responsive to cabinpressure,- the other responsive to changes in the difference betweencabin pressure and flight pressure whereby a pressure differential isobtained between flight ailtitude pressure and cabin-pressure, the saiddifierential being controlled by the opening and closing or said outletvalve .in response to pressure reactions of said coacti unit's and aslag means comprising-a rate or climb meter se'nsitive to' cabinpressure said climbimeter acting, in --eventofcrapid chan es in flightain'- tude pressure such as rapid climb or descent,- to override thecontrolof the regulator mm-respect to said outlet valve'and preventasimilarly rapid change in cabin pressure by dimitingthe cabin pressurechange to :a :set irate :compatiblefiwith physiological comfort.

6. In .an aircmft', a=cabin1adapted sto be supercharged, a ramming airintalreductsleadingtothe cabin, at least one blower adapted :to increasethe pressure of the iincomingair, anoutlet'walve adiustablexo rvaryrthecabmqanessurewith respect to the incoming Fblower pressure; a regulatingdevice sensitive to pressuremiiferences hetweell flight altitudepressure andcabin pressure and adapted to control said mitletovalve tomaintain aip'redetermined ratiwb'etween cabin pressureand flightaltitude ':pressure as gaugedfirmun. a set equalizing altitude pressure,a servonrotor. actuated in response to pressure variations regulatingdevice, said servomotorxoperating-said outlet valve, a second servomotor:for varying the delivery of the said supercharging blower, means withinthe said outlet valveior-coertrolling the second said servomotona valvemeans controlling "the reaction "of flight pressure upon the saidregulating device whereby the rapidity of cabin pressure changes my bevaried or halted with respect to :fiight altitude pressure changes, :and:atrate :of Fc'limb zneteradapted to :control the rate of decrease orincrease of cabin pressure irrespective of the rate or 'flightzaltitudepressure decrease or iincreasersuch control :being accomplishedibyoverriding .the influence-of dihesaid regulating in the control :of saidservomotor operating'said outlet valve.

'7. Acabin pressure regulating device comprising an adjustable dial foran altitude at whichrcazbin pressure'will be equalized with flightpressure, apa'ir of spaced contacts, a :pair' of coacting pressuresensitive units, a i'ever pivotally :comrected to -said pmssurcFsensitrve units and adaptedror contacting either or-nather of saidspaced contacts, and meahswonneoted with the said dial for .relativel yadjusting the said contacts and lever, "the conibmation being responsive.tocabin pressure and xlightpressure and operative'to maintainthecabinmressuresubstahtially at a autioaor equallizmgquessurennnus:flightpressure .to :equalizmg pressurenznanusnabm pressure.

i8. A :cabin pressure regulating :device compris- 752mg anarljnstaibleldial am'altrtude :at

' 1 5 which cabin pressure will be equalized with flight pressure, apair of spaced contacts, a pair of pressure sensitive units, a leverconnecting the sensitive units and a lever indirectly connected to thefirst said lever and adapted to contact either or neither of the saidspaced contacts, and a third lever adapted to move relatively to thefirst said lever and the second said lever, for the purpose of changingthe fulcrum of the first said lever as it moves, whereby the effect ofreactions of the said pressure sensitive units may be varied withrespect to the second said lever moving between the spaced contacts, thecombination being sensitive to caoin pressure and flight pressure andoperative to maintain, the cabin pressure at a predetermined ratio tothe flight pressure as gauged from a set equalizing pressure.

9. In an aircraft, a cabin adapted to be supercharged and having anoutlet, blower means for supplying air to said cabin at a pressurehigher than that of the ambient flight atmosphere, air flow controlmeans for varying the cabin pressure, rate of climb regulator means togovern the rate of decrease or increase of cabin pressure, means forvarying the rate of decrease or increase as governed by said regulatormeans, means for limiting cabin pressure to a set pressure altitude,means for varying the said pressure altitude, and a servo systemoperative upon said airflow control means and responsive to saidregulator. means and said pressure limiting means to control the saidair flow.

10. In an aircraft, a cabin adapted to be super charged and having anoutlet, a blower for supplying air to said cabin at a pressure higherthan that of the ambient flight atmosphere, a valve i fir l fl llautletalate of climb meter sensitive to cabin pressure, means for adiustablysetting said meter to govern the rate of decrease or increase of cabinpressure, an altimeter sensi- 1 tive to cabin pressure, means foradjustably setting a limiting cabin pressure, and a servo systemresponsive to said climb meter and said altimeter for opening andclosing said outlet valve, thereby controlling the pressure in saidcabin in accordance with the settings of said climb meter and saidaltimeter.

11. In an aircraft, a cabin adapted to be supercharged and having acontrollable outlet, a blower for supplying air to said cabin atapressure higher than that of the ambient flight atmosphere, a rate ofclimb meter sensitive to cabin pressure and having adjustable means forsetting a cabin pressure rate of decrease and increase, a primary servosystem responsive to said rate of climb meter for opening anr closingsaid controllable outlet, thereby controlling cabin pressure rate ofdecrease and increase, an altimeter sensitive to cabin air pressure andhaving adjustable means for setting a limiting cabin pressure altitude,and a secondary servo system responsive to said altimeter for overridingsaid primary system when the cabin has attained the set pressurealtitude.

12. In combination with an aircraft pressure cabin, means to supply airunder pressure within the cabin, normal means to regulate and vary thepressure therein automatically under the influence of and generally inaccordance with change of external pressure, auxiliary means, includinga rate-of-pressure-change element, operable automatically under theinfluence of change of cabin pressure to overrule said normal means andto limit the rate of pressure change, and means always operable tooverrule '16 the normal means and the auxiliary means to limit thepressure difference between cabin pressure and external pressure to apreselected one.

13. Mechanism for controlling change of pressure within an aircraftcabin, comprising means operable to create and control a difierence ofpressure within the cabin over the external pressure, an air chamberwithin said cabin having a restricted opening in it, a wall movableunder the influence of a pressure difference internally and externallyof the air chamber, due to a change of pressure within the cabin at arate in excess of the capability of the restricted chamber opening torelieve the pressure within the air chamber, and means operativelyassociated with said movable wall, and operatively connected to saidfirst means to govern its operation for limiting the rate of pressurechange within the cabin.

14. Pressure control means for a chamber exposed to varying exteriorpressures, comprising valve means communicating the interior ofsaidchamber with the exterior thereof, a motor for operating said valvemeans, and a rate of pressure change device in said chamber comprising apressure sensitive element having one side thereof in directcommunication with the pressure within said chamber and the other sidethereof in restricted communication with said chamber pressure, whereby,upon a predetermined rate of change of pressure within said chamber,said element is actuated to energize said motor to voperate said valvemeans to close communication between the interior and exterior of saidchamber.

15. In an aircraft cabin, a vent valve, a motor for operating saidvalve. first pressure-sensitive means responsive to cabin pressure onone side and sub-atmospheric pressure on its otherside operativelyconnected to actuate said motor, second pressure-sensitive meansresponsive to cabin pressure on one side and to atmospheric pressure onits other side also operatively connected to actuate said motor, andpressure-responsive means having one side thereof directly subjected tocabin pressure and the other side thereof in restricted communicationwith said cabin operatively connected to said motor to override saidfirst and second means when cabin pressure changes at excessive ratesduring changes in the altitude of flight.

16. Mechanism for regulating the pressure within an aircraft body forhigh altitude flights, and adapted to be sealed at high or mediumaltitudes against escape of pressure from within, under the influence ofa pressure differential above the ambient pressure at such altitudes,comprising means operable to create such a pressure differential withinthe sealed cabin, a rateof-pressure-change element responsive to changeof pressure within the cabin, means operable at will, in anticipation ofa change in altitude, and consequent change in cabin pressure, to inducea change in cabin pressure for altering such pressure differential,independently of the rate of change of the ambient pressure, due tochange or lack of change of altitude, and means controlled by saidrate-of-change element for governing said inducing means to limit therate of change of pressure within the cabin during such inducingoperation.

1'7. Mechanism to control aircraft cabin pressures comprising, incombination with means to supply air under pressure to the cabin,differential-pressure responsive means operable atall altitudes toprevent the cabin pressure exceeding a selected pressure above theexternal pressure, absolute-pressure responsive means subject to cabinabsolute pressure operable at a selected altitude to maintain cabinpressures substantially constant, up to the limit of differentialpressure set by the differential-pressure responsive means, and meansoperable at will, and overriding the absolute-pressure responsive means,but subject to the limiting control of the differential-pressureresponsive means, to effect or control the rate of change of cabinpressure.

18. Mechanism to control aircraft cabin pressures, comprising, incombination with means to supply air under pressure to the cabin, anormal automatic control system including an absolutepressure responsivemeans automatically'operable at a selected altitude to initiate anincrease of cabin pressure relative to external pressure, and adifferential-pressure responsive means automatically operable at allaltitudes to prevent increase of cabin pressure beyond a selecteddifferential over external pressure, and therefore at a-given altitudeimposing a maximum limit on the increase initiated by theabsolute-pressure responsive means, and controlling cabin pressures ataltitudes above such given "altitude, and further in combinationtherewith a manual control system including means to override at willthe absolute-pressure responsive means and to initiate a change of cabinpressure, whether rise or fall, independently of altitude, but arrangedto be limited by the diiferential-pressure responsive means, whereby thedifierential limit set by the latter is never exceedd-by-the manualcontrol system nor by the automatic control system.

19. Mechanism to control aircraft cabin pressures, comprising, incombination with means to supply air under pressure to the cabin, and anoutlet to discharge air from the cabin, valve means operable to controlair movement through and pressure within the cabin, means operableautomatically, to operate-said valve means to maintain a substantiallyconstant cabin pressure, diiferential-pressureresponsive means operableautomatically at all times upon the attainment of a selecteddifferential of cabin pressure above external pressure for limiting suchdifierential to the selected value, and means manually operable at alltimes to operate said valve means to decrease outflow and thereby toincrease cabin pressure above such substantially constant value, or toincrease outflow and-thereby to decrease cabin pressure below suchsubstantially constant value, between a lower limit fixed by theexternal pressure, and an upper limit fixed by saiddifferen'tial-pressure responsive means, and at a selected rate ofpressure change.

20. In combination with an aircraft pressure cabin, normally operablemeans to maintain 'the pressure therein substantially equal to externalpressure up to a selected altitude, to 'substantially maintain withinthe cabin-a pressure'corresponding to such selected altitude duringflight between that altitude and a selected higher altitude, and'tomaintain substantially the attained'dififer entiai of cabi'n'p'res'su'rcover ambient pressure during flight above the'second selected altitude,and auxiliary controlmeans operable to limit the rate of cabin pressurechange in flight froma higher to a lower altitude, or vice versa,independently of and regardless of the rate of cabin pressure changewhich would "otherwise be "imposed by the normal control means at therate of descent or ascent chosen 21. In combination with an aircraftpressure cabin, normally operable means to maintain the pressure thereinsubstantially equal to external pressure up to a selected altitude, tosubstantially maintain within the cabin a pressure corresponding to suchselected altitude during flight between that altitude and a selectedhigher altitude, and to maintain substantially the attained diiierentialof cabin pressure over ambient pressure during flight above the secondselected altitude, auxiliary control means operable to limit the rate ofcabin pressure change in flight from a higher to a lower altitude, orvice versa, independently of and regardless of the rate of cabinpressure change which would otherwise be imposed by the normal controlmeans at the rate of deace-nt or ascent chosen, and means to adjust theauxiliary control means to select and effect control at different rateof pressure change.

22. In combination with an aircraft pressure cabin structure having aknown resistance to bursting under the influence of a higher pressureinternally than externally, means to supply air under pressure withinthe cabin, means operable to control and produce a pressure differentialof cabin pressure over external pressure, a rate-ofpressure-changecontrol to govern the action of the pressure controlling means'andthereby to govern the rate of pressure change Within the cabin,regardless of change or rate of change of external pressure, and adifferential-pressure control means operative to limit the pressuredifference possible of attainment to a safe value within the burstingstrength of the cabin structure.

23. Mechanism for controlling change of pressure within an aircraftcabin; comprising pressure-responsive means operable automatically toeffect a change of cabin pressure, and thereby to establish a pressuredifferential between the pressure within the cabin and the exterioratmospheric pressure, and a rate-of-pressurechange element responsive torapid change of pressure within the cabin and operativcly connected tothe differential-establishing means, whereby upon such rapid rate ofpressure change it is automatically operable to retard the action ofsaid pressure-responsive means, thereby to limit the rate of pressurechange within the cabin.

24. Mechanism to control aircraft cabin pressure, comprising, incombination with means to supply air under pressure to and to dischargeair from the cabin, three pressure responsive means. one whereof issensitive to the pressure differential of cabin pressure over externalpressure, and always operable to prevent such differential exceeding aselected value, the second operable to regulate cabin pressure withinthe diflerential thus determined, and the third being sensitive to rateof pressure change, to restrict any change of pressure, within thepredetermined differential, automatically to a predetermined rate,independently of the rateof air supply to or discharge from the cabin orthe actual difierence between cabin pressure and external pressure orthe rate of change of such difierence.

25. Mechanism to control aircraft cabin pressure, comprising, incombination with means to supply air under pressure to and to dischargeair from the cabin, three pressure responsive means, one whereof issensitive to the pressure differential of cabin pressure over externalpressure, and always operable to prevent such differential exceeding aselected value, the second 0per- 19 able to regulate the cabin pressurewithin the differential thus determined, and the third being sensitiveto rate of pressure change, to restrict any change of pressure, withinthe predetermined differential, automatically to a predetermined rate,independently of the rate of air supply to or discharge from the cabinor the actual difference between cabin pressure and external pressure orthe rate of change of such difference, and means to adjust said thirdpressure responsive means, to preselect any one of various rates ofpable of flight at high altitudes, and having a cabin structurallyformed to resist an allowable pressure difference between cabin pressureand external pressure, which pressure difference is not in excess of afraction of the total pressure difference between sea level and theaircrafts ceiling, means operable to create a pressure differentialwithin the cabin, not greater than the structurally allowable pressuredifference, an element subject to cabin pressure, and sensitive to rateof change thereof, and means operable in re- *sponsetotherate-oepressure-change element to prevent pressure change inresponse to said first means at a rate in excess of a predeterminedrate.

28. In combination with an aircraft capable of flight at high altitudes,and having a cabin structurally formed to resist an allowable pressuredifference between cabin pressure and external pressure which is not inexcess of a fraction of the total pressure difference between sea leveland the aircrafts ceiling, means to supply air under pressure within andcontinuously to discharge such air from the cabin, to decrease suchpressure difference, means to control the cabin pressure tosubstantially maintain it at a value which, with relation to externalpressure, is not greater than the allowable pressure diiference, andmeans operable to regulate the rate of pressure change within the cabin,regardless of whether such change occurs by reason of ascent or descent,and consequent change of external pressure, or by reason of change inthe rate of supply of air under pressure, or by reason of change in therate of discharge of air from the .cabin.

29. A pressure control device for controlling the pressure in the cabinof an aircraft comprising, in combination, means forming a port, a valvemember movable relative to said portforming means for controlling flowof fluid through said port, a bellows held stationary at one end andconnected at its other end to a movable connecting element, a secondbellows connected at one end to said movable connecting element andhaving at its other end an operative association with said valve elementsuch that movement of said other end controls the movement of said valveelement, means for subjecting the exterior of both of said bellows tocabin pressure, and means for subjecting the interior of 2O one of saidbellows to ambient pressure, the other bellows being evacuated.

30. A pressure control device for controlling the pressures in the cabinof an aircraft comprising, in combination, means forming a port, a valvemember movable relative to said portforming means for controlling flowof fluid through said port, a bellows held at one endstationary andconnected at its other end to a movable element, an evacuated bellowsconnected at one end to said movable element and operatively connectedat its other end to said valve member, means for subjecting the exteriorof both of said bellows to cabin pressure, and means for subjecting theinterior of said first bellows to ambient flight pressure.

31. A pressure control device comprising, in combination, a port, avalve seat surrounding said port, a valve member cooperating with saidvalve seat for controlling the flow of fluid through said port, andpressure responsive means for controlling the operation ofsaid valvemember, said pressure responsive means including a pressure responsivemember operatively connected to said valve member and subjected on oneside to the pressure at one side of said valve seat and on its oppositeside to a subatmospheric pressure, and a second pressure responsivemember connected to said first pressure responsive member and actingthrough the latter on said valve member, saidsecond pressure responsivemember subjected continuouslyon opposite surfaces thereof to thepressures at opposite sides of said valve seat.

3 2. In a device for controlling the cabin pressures of an aircraft,valve means adapted to vent the cabin interior, means for controllingsaid valve means, a device responsive to cabin pressures and operativeon reduction of cabin pressure to a value corresponding to apredetermined height for transmitting movement to said control means toaffect control of said valve means to vary venting to seek to maintainthe cabin pressure substantially constant, and a device responsive tothe differential in pressure between the cabin pressure and the exteriorpressure for actuating said means controlling said valve means andoperative at a predetermined pressure differential for furthertransmitting movement to said valve control means to vary venting, saiddevices so arranged with respect to each other that one of said devicestransmits its individual valve positioning movements to said valvecontrol means through the other device, and the latter device reactsagainst the former when transmitting its individual valve positioningmovements to said valve control means.

33. In a device for controlling the cabin pressures of an aircraft,valve means adapted to vent the cabin interior, pressure responsivemeans operative on reduction of cabin'pressure to a value correspondingto a predetermined altitude for actuating said valve means to varyventing to seek to maintain the cabin pressure substantially constant,and asecond pressure responsive means responsive to the differential inpressure between the cabin pressure and the exterior pressure forfurther actuating said valve means to vary venting, each of saidpressure responsive means embodying an expansible chamber controldevice, one operatively connected to said valve means and the otherdevice yieldingly connected to operate said valve means through thefirst device, one of said control devices having one side thereofsubjected to the cabin pressure aria-p90 2'1" and the opposite side to asubatmospheric pressure and said other control device having one sidethereof subjected to cabinpressure and its opposite side subjected toatmospheric pressure.

34. Asealed cabin for an aircraft provided with valve -meanscommunicating the interior of the cabin with theexterior thereof, andmeans comprising'apressure sensitive element having one side-thereof indirect communication with said cabin pressure and an opposite sidethereof in restricted communication withsaid cabin pressure responsiveto and actuated during a predetermined rate of change of pressure withinsaid cabin during a rapid rate of climb or descent of said craft whensaid valve means is open for operating said valve means to closecommunication between the interior and exterior of said cabin.

35. Mechanism for controlling change of pressure within an aircraftcabin, comprising'means operable to create and control a difference-ofpressure 'within the cabin over the external pressure, an air chamberwithin said cabin having a restricted opening in it, a wall movableunder.

the influence of a pressure difierenceinternally interior of thecompartment withFthe exterior thereof, control means for operating saidvalve means to maintain the pressures within the fcom partment atpredetermined values-with respect to varying exterior pressures, andmeanshaving one side thereof in direct communication with thecompartment pressure and anopposite side thereof in'restrictedcommunication with the compartment pressure operativeduringa'predetermined rate of change of pressurewithin said compartmentwhen the compartment interior and exterior are in communication forcontrr'illing said valve means independently of said control means.

37. An aircraft compartment having blower means therefor, valve meanscommunicating the interior of the compartment with the exterior thereof,control means for operating said valve means to maintain the pressureswithin the compartment at predetermined values with respect to varyingexterior pressures, and a rate of change of pressure device having, oneside thereof indirect communication with the compartment pressure and.an. opposite side thereof in restricted communication with thecompartment pressure operative during a predetermined rate of change ofpressure within said compartment when the compartment interior andexterior are in communication for closing said valve means.

38. Pressure control means for a. chamber exposed to varying exteriorpressures, comprising valve means communicating the interior of 'saidchamber with the exterior thereof, and'means comprising a resilientmember having one side thereof in direct communication with said chamberpressure and an opposite side thereof in restricted communication withsaid chamber pressure responding to a predetermined rate of pressurechange within said chamber when said chamber interior and exterior arein communication for operating said valve means to close 22?:communication between the interior and exterior of said chamber.

39. Pressure control means for a chamber exposed to varying exteriorpressures, comprising valve means communicating the interior of saidchamber with the exterior thereof, and means including a compressibleand expansible member having the inside thereof in restricted communication with'the chamber pressure and the outside thereof in directcommunication with the chamber pressure responding to a predeterminedrate of pressure change within said chamber "when said chamber interiorand exterior are inv communication for operating said valve means toclose communication between the interior and exte'rior of said chamber.

{10. An aircraft having a compartment provided with valve meanscommunicating the interior of the compartment with the exterior thereof,a reversible motor for operating said valve means, and means including apressure sensitive resilient member having'oneside thereof indirectcommunication with the pressure within said chamber and the otherside thereof in restricted communication-with said chamber pressure,whereby; upon a predetermined rate of pressure change within saidchamber during a rapid rate of climb of said craft,said member isactuated to energize said 'motor to operate said valve means to closecommunication between the interior and exterior of saidcompartment. l

' 41-. An aircraft having a compartment provided with valve meanscommunicating the interior of the compartment 'with the exteriorthereof, and means ir'icluding'--' a pressur'e sensitive element havingone side thereof in direct --"communica tion with the pressure witlnnsaid'eompartment aridf'the-other side thereof in restricted com"muni'cation 'withsaid compartment pressure, whereby, upon sudden chamberpressure decrease causing a'predeterminedrate of change of pressurewithinsaidcompartment during a rapid rate of climb of said craft,saidelement is actuated in one direction'tooperate said valve means toclose communication betw'eenthe interior and exterior of saidcompartment, andwhereby, upon a sudden compartment pressure increasecausing a predetermined rate of change of pressure within saidcompartment during a rapid rate of descent of said craft, said elementis actuated in a second direction to operate said valve means tolikewise close communication between the interior and exterior ofsaid-compartment.

42. An aircraft sealed compartment having blower means therefor, valvemeans communieating the interior of the compartment with theexteriorthereof, electrical means for said valve means, control meansfor energizing said electrical'meansto actuate said valve means .0maintain the pressure, within said compartment in a predeterminedrelation with respect to the pressure exterior of said compartment, andmeans comprising'a' resilient member having one side thereof in directcommunication withsaid compartment pressure and an opposite side thereofin restricted communication with said compartment pressure actuatedduring a predetermined rate .of change of pressure within saidcompartment for energizing said electrical means to operate saidlvalvemeans and close communication between the interior and exterior of saidcompartment.

43. A sealed cabin for an aircraft provided with valve meanscommunicating the interior of the cabin with the exterior thereof, andmeans comprising a pressure sensitive element having one side thereof indirect communication with said cabin pressure and an opposite sidethereof in restricted communication with said cabin pressure responsiveto and actuated during a predetermined raterof change of pressure withinsaid cabin during a rapid rate of climb or descent of said craft whensaid valve means is open for operating said valve means to closecommunication between the interior and exterior of said cabin.

44. In a system of pressure controlfor a sealed chamber, acontinuouslyenergized blower means for building up pressure in saidchamber, valve means providing communication between the inside andoutside of said chamber, control means within said chamber for operatingsaid valve means to maintain the pressure within said chamber atpredetermined var ing values with respect to a varying exterior chamberpressure, and rate of change of pressure means including a pressuresensitive element having one side thereof in direct communication withthe pressure within said chamber and the other side thereof inrestricted communication with said chamber pressure, whereby, 'upon apredetermined rate of change of pressure within said chamber saidelement is actuated to operate said valve means and close communicationbetween the interior and exterior of said chamber. 1 45. A sealedcabinfor anaircraft having a continuously energized blower for building uppressure within said cabin, valve-means for normallycommunicating theinterior of the cabin with the exterior thereof, a reversible motor foroperating saidfvalve means, means including a pressurewensitiveelement-respondin to cabin ipressurebnlyandasecond pressure sensitiveelement responding to the differential of the cabin pressure and theatmospheric pressure outside thereof for energizing said motor in onedirection to operate said valve means when the pressure within the cabinhas reached a predetermined value to close communication between theinterior and exterior of said cabin, said elements being operative toenergize said motor in the opposite direction opening said valve meansto permit communication of the interior of said cabin with the exteriorthereof when the pressure built up by said blower exceeds apredetermined amount, and means, including a pressure sensitive elementsubjected on one side to cabin pressure and on the opposite side to avolume of air in restricted communication with the interior of saidcabin, operative during a predetermined rate of change of pressurewithin said cabin for energizing said motor to close said valve means.

46. An aircraft cabin pressure control system comprising means fordelivering air to said cabin under a pressure greater than ambientflight pressure, avalve for discharging air from said cabin, means foroperating said valve to vary the rate of air discharge from said cabinrelative to the rate of air delivery to said cabin whereby the absolutepressure within said cabin may be varied, a first pressure sensitivemeans responsive to changes in cabin absolute pressure operativelyconnected to said valve operatin means and adapted to actuate the sameto seek to maintain cabin absolute pressure substantially constant, asecond pressure sensitive means responsive to changes in the differencebetween cabin absolute pressure and ambient flight pressure, and meansoperatively interconnecting said second pressure sensitive means andsaid valve operating means for progressively opposing the action of saidfirst pressure sensitive means on said operating means as ambient flightpressure decreases to thereby impose a conjoint action resulting fromchanges in cabin absolute pressure and cabin differential pressure onsaid valve operating means whereby cabin differential pressure will becontrolled to change substantially inversely proportional to changes inambient flight pressure.

47. An aircraft compartmentpressure control comprising means fordelivering air to said compartment under a pressure greater than ambientflight pressure, means for discharging air from said compartment, meansfor varying the rate of air discharge from sair compartment relative tothe rate of air delivery to said compartment whereby the absolutepressure within said compartment may be varied, means, including a firstcapsule subject to cabin absolute pressure and a second. capsule subjectto cabin differential pressure coacting through an interconnectingmeans, made operative upon said aircraft reach altitude at which saidcontrolling means is made operative, said preselecting means beingchangeable during flight of said aircraft and operable independently ofsaid control. means whereby said pressure altitude at which said controlmeans is made operative may be altered during flight of :said aircraftwithout altering thei said proportion.

48. An aircraft compartment pressure control comprising means fordelivering air to saidcon rpartment under a pressure greater thanambient flight pressure, means for discharging air'from saidcompartment, means for varying the, rate of air discharge from saidcompartment relative to the rate of air delivery to said compartmentwhereby the absolute pressure within said compartment may be varied,means, including .a first capsule subject to cabin absolute pressureanda second capsule subject to cabin differential pressure coacting throughan interconnecting means, made operative upon said aircraft reaching apredetermined pressure altitude for controlling said last named meansfor regulating the absolute pressure in said compartment 'in such amanner as to change said absolute pressure directly proportional tochanges in ambient flight pressure. WOLFGANG B.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

